The present embodiments relate to an angiographic examination method for depicting a target region inside a patient with a vascular system as an examination object.
An angiography system for the performance of an angiographic examination method is known, for example, from U.S. Pat. No. 7,500,784 B2, which is explained below based on FIG. 1.
FIG. 1 shows a monoplanar X-ray system depicted as an example with a C-arm 2 held by a stand 1 in the form of a six-axis industrial or articulated robot. The X-ray system includes an X-ray source (e.g., an X-ray emitter 3 with X-ray tube and collimator) and an X-ray image detector 4 being attached to ends of the C-arm 2 as an image recording unit.
Using the articulated robot known, for example, from U.S. Pat. No. 7,500,784 B2, which may have six axes of rotation and thus six degrees of freedom, the C-arm 2 may be displaced spatially, as required, being rotated, for example, about a center of rotation between the X-ray emitter 3 and the X-ray image detector 4. The angiographic X-ray system 1 to 4 is rotatable, for example, about centers of rotation and axes of rotation at the C-arm plane of the X-ray image detector 4 (e.g., about the center of the X-ray image detector 4) and about axes of rotation intersecting the center of the X-ray image detector 4.
The known articulated robot has a baseframe that, for example, is permanently mounted on a floor. To this, a carousel is rotatably attached about a first axis of rotation. Attached to the carousel so as to pivot about a second axis of rotation is a robot rocker arm, to which a robot arm that may rotate about a third axis of rotation is fixed. A robot hand is attached at the end of the robot arm, so as to rotate about a fourth axis of rotation. The robot hand has a fixing element for the C-arm 2, which may pivot about a fifth axis of rotation and may rotate about a sixth axis of rotation extending perpendicular thereto.
The implementation of the X-ray diagnostic device is not dependent on the industrial robot. Normal C-arm devices may also be used.
The X-ray image detector 4 may be a rectangular or square, flat semiconductor detector that may be made of amorphous silicon (a-Si). Integrating and possibly counting CMOS detectors may also be used, however.
Located in the beam path of the X-ray emitter 3 on a tabletop 5 of a patient positioning couch is a patient 6 to be examined as an examination object. On the X-ray diagnostic device, a system control unit 7 is connected to an image system 8 that receives and processes the image signals from the X-ray image detector 4 (e.g., operating elements are not shown). The X-ray images may be viewed on displays of a monitor bracket 9. The monitor bracket 9 may be held by a ceiling-mounted support system 10 with a cantilever arm and a lowerable support arm, may travel lengthwise, pivot and rotate, and is height-adjustable. Also provided in the system control unit 7 is an apparatus 11, the function of which is further described below.
Instead of the X-ray system illustrated by way of example in FIG. 1 with the stand 1 in the form of the six-axis industrial or articulated robot, the angiographic X-ray system may also have a normal ceiling- or floor-mounted bracket for the C-arm 2.
Instead of the C-arm 2 shown by way of example, the angiographic X-ray system may also have separate ceiling- and/or floor-mounted brackets for the X-ray emitter 3 and the X-ray image detector 4, which, for example, are electronically fixedly coupled.
The X-ray emitter 3 emits a beam of radiation 12 originating from a beam focus of an X-ray radiation source of the X-ray emitter 3. The beam strikes the X-ray image detector 4. If 3D data sets are to be generated in accordance with the DynaCT method (e.g., a method for rotational angiography), the rotatably mounted C-arm 2 with X-ray emitter 3 and X-ray image detector 4 is rotated such that, as shown schematically in FIG. 2 by the aerial view of the axis of rotation, the X-ray emitter 3 (e.g., represented by a beam focus) and the X-ray image detector 4 move in an orbit 14 about an object 13 to be examined that is located in the beam path of the X-ray emitter 3. In order to generate a 3D data set or volume data set, the orbit 14 may be full or partial.
In accordance with the DynaCT method, the C-arm 2 with X-ray emitter 3 and X-ray image detector 4 may move by an angular range of at least 180° (e.g., 180° plus fan angle), and records projection images in rapid succession from various projections. The reconstruction may be performed using just one section of this recorded data.
The object 13 to be examined may, for example, be an animal body, a human body, or a phantom body.
The X-ray emitter 3 and the X-ray image detector 4 each move about the object 13 such that the X-ray emitter 3 and the X-ray image detector 4 are positioned at opposite sides of the object 13.
In normal radiography or fluoroscopy using an X-ray diagnostic device of this type, the medical 2D data of the X-ray image detector 4 may be buffered in the image system 8 and subsequently displayed on the monitor bracket 10.
Angiography systems of this type are used in the field of fluoroscopy-controlled, interventional repairs to abdominal aortic aneurysms.
An abdominal aortic aneurysm (AAA) or aneurysma verum aortae abdominalis is a vascular dilatation on the abdominal aorta, a widening of the abdominal aorta below the branching of the renal arteries in the anterior/posterior diameter of over 30 mm. This is treated by using a stent graft. By way of both groins, guide wires and catheters are inserted into the aorta. Via this, one or more stent grafts (i.e., composite vascular stents) are inserted (see FIG. 3), as shown, for example, in Cardiology Today, January 2011, page 36.
The purpose of using these stent grafts is to position the landing zone of the vascular prosthesis as far as possible in the healthy vascular wall area without coinciding with any important vascular branchings. For example, the branchings of the renal arteries, of the superior mesenteric artery (e.g., arteria mesenterica superior), of the truncus c(o)eliacus, and of the internal iliac artery (e.g., arteria iliaca interna) are to be kept free. A sensitive point is the placement of the “main stent” in the aorta, during which the vascular branchings mentioned are not to be blocked. Even with relatively simple stents, which, for example, in addition to the aorta, merely encompass the femoral arteries, the final stent often is to be made up of a “main stent” and “part-stents”. Thus, for stents for the femoral arteries, the common iliac arteries (e.g., arteriae iliacae communes) are normally “flange-mounted” onto an aortic stent acting as a main stent, as is explained below based on FIG. 3. In more complex stents, known as fenestrated or branched stents, other part-stents are added as well. Methods for supporting these procedures using anatomically correct overlaying of, for example, presegmented CT data are being trialed and show the physician the aorta and branching vessels in the form of a permanent roadmap, as described, for example, in DE 10 2011 005 777 A1.
In order not to have to inject contrast agent for the permanent display of vessels for control purposes during the complex stent positioning, a reference image may be overlaid in an anatomically correct manner to assist with positioning. This shows the vessels (e.g., in the case according to FIG. 5, the aorta and branching vessels). This reference image may be either a 2D angiography (DSA) or a previously recorded 3D data set (e.g., a CT angiography) of the aneurysm. These show more details and may be overlaid using any angulations of the C-arm.
A problem with these overlays is that the reference image (2D or 3D) shows the vascular anatomy at a particular point in time. If, for example, the physician introduces very inflexible or rigid medical instruments (e.g., catheters), the anatomy of the vessels deforms. If this deformation is not corrected in the overlaid reference image, this produces an inaccuracy or “incongruity” in the overlay, as further explained below. This may result in uncertainties in the navigation during a subsequent intervention, in which the overlay serves as an aid to navigation.
DE 10 2010 012 621 A1 has already proposed a way of interoperatively correcting such deformations, in which the medical instrument is located or reconstructed from two X-ray projections.
This method for deformation equalization involves adaptation of a reference image, which automatically corrects displacements that may occur as a result of inserting medical instruments (e.g., when using a stent in an aorta). In this way, the displacements that may not initially be perceived in the image because of the angle of view may be corrected.